Degradable animal chewing article possessing enhanced safety, durability and mouth-feel

ABSTRACT

A chewable, biodegradable article for use as a pet toy comprises a matrix made of a natural polymer, a synthetic organic polymer or a mixture thereof, a natural or synthetic fibrous material that comprises fibers and that is bonded chemically or physically with the matrix material, and, optionally, includes one or more microbe inhibiting agents that inhibit the growth of microbes in or on the article. The presence of the fibrous material inhibits formation of sharp edges upon breakage when the article is chewed, thereby rendering the article safer when used by pets. Also disclosed are processes for manufacturing the above article.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.09/578,199, filed May 24, 2000, now U.S. Pat. No. 6,576,246, whichclaims the benefit of U.S. provisional patent application Ser. No.60/135,672, filed May 24, 1999.

BACKGROUND OF INVENTION

1. Field of the Invention

The invention relates to chewable articles intended primarily as chewtoys for dogs or other domestic animals.

2. Description of the Background Art

Chewable animal articles such as artificial bones for dogs have beenmade of many materials and in many configurations and sizes. These havebeen made of compressed natural or food materials with a binding agent;some are made of synthetic polymers, as polymers mixed with protein(U.S. Pat. No. 4,681,758), nylon (U.S. Pat. No. 3,871,334) orpolyurethane (U.S. Pat. Nos. 4,557,219 and 4,513,014).

Chewable articles are frequently constructed from degradable materialsthat possess at least a substantial component which degrades orotherwise diminishes substantially in structural integrity with usageand over time. The degradation, typically accelerated by the chewingaction of the animals, is frequently accelerated by exposure to themoisture and/or digestive enzymes in saliva. The durability of sucharticles is therefore intrinsically limited.

If a chewable article is too soft, it is too easily ripped apart orshredded during use. On the other hand, if the article is too hard, itmay tend to crack, shatter, or splinter. This tendency to splinter uponbreakage or when otherwise structurally damaged is highly undesirable.Splintering leads to sharp edges that can cause injury and lead serioushealth problems for the animal, especially if sharp-edged material isswallowed. Moreover, small pieces breaking from the articles may also beswallowed and contribute to health problems.

Of the digestible type of mastication article, rawhide is the mostpopular type of mastication article (e.g., U.S. Pat. Nos. 5,114,704;5,310,541; 5,476,069). Simulated rawhide mastication articles compriseoil seed protein, a polyol plasticizer, lecithin, and water, extrudedinto a ribbon (U.S. Pat. No. 4,419,372).

U.S. Pat. No. 5,407,661 discloses a digestible mastication article for apet in which a starch, a cellulosic fibrous material (e.g., corncobfractions), a humectant, a proteinaceous binder and a tarter-controloral care additive. U.S. Pat. No. 5,419,283 discloses a moldedmastication article comprising a starch material and a biodegradableethylene copolymer. Other edible materials can be added as plasticizersor as lubricants. These materials are mixed in the presence of water forsubsequent injection molding into desired shapes (e.g., a bone).

U.S. Pat. No. 5,477,815 discloses a molded dog mastication articlecomprising water absorbing nylon in which at least a surface layer hassugar incorporated therein.

U.S. Pat. No. 5,485,809 discloses animal chewing toys that shave awaywhen chewed without puncturing, cracking, splintering or shattering,while providing satisfaction to the chewing animal. The chewing actionis said to produce a desirable roughening and bristling of the surfacethat scours and cleans the animal's teeth. Flavoring material isuniformly dispersed throughout the body of the toy rather than just onthe surface. The article is made from an ethylene/methacrylic acidcopolymer, ionically cross-linked ionomer resin. This document disclosesa desirable range of hardness (on a “D” scale—from 65 to 99, preferredrange from 75 to 85).

U.S. Pat. No. 4,364,925 ('925) discloses chew-resistant products madefrom feed particulates with supporting fibers incorporated into the foodcomponents prior to compacting. Chew resistance is controlled primarilyby the amount of such fibers. A multilayer article comprises at leastone layer of a higher chew-resistance than the other layer, controlledby the amount and type of structure-supporting fibers. For example,supporting fibers are incorporated in the base layer of dry dog food andthen a second layer is prepared without such fibers to yield amultilayer article having an inner hard, chew-resistant layer and anrelatively soft and crumbly exterior layer. Alternatively, an innerlayer is prepared without supporting fibers and a second layer withfibers is superimposed, leading to a hard exterior layer and softinterior layer. By starting with a soft-core layer and alternating thetype of layers, multiple alternating harder and softer layers areproduced. Such materials can serve as chew-resistant products that aresufficiently hard to exercise a pet's teeth and jaws and to removeplaque and tartar.

Suitable structure-supporting fibers are said to be any fibers thatperform the function of binding the food into a unitized chew-resistantproduct and are not harmful. Such fibers may or may not be digestible bythe animal. Safely digestible fibers include collagen. Indigestiblefibers include cellulosic fibers or mixtures of animal-based digestiblefibers and such indigestible fibers. Suitable sources of digestiblefibers are animal tissue for example, skin, muscles, tendons,intestines, etc. The amount of animal hide material used as a source ofcollagen depends upon factors such as the type and amounts of fibers inthe hide, the type of food in the product, whether swollen or unswollencollagen or hide binders or gels are employed, etc. As defined in thisdocument, “collagen” includes other fibrous protein such as elastin,reticulin, etc. The bundles of fibers are said to be theoreticallybroken and realigned to form fiber interlocks. For maximum strength thecut fibers re-interlock in the final product so that relativelycontinuous fiber linkage bonds are maintained. Useful collagen fibersinclude those obtained from hides as well as those prepared bydissolving protein, precipitating the protein from solution and aligningthe molecules to obtain a fibrous material. Protein fibers may also bederived from soy protein, egg white, wheat gluten, etc. The fibrous formof these proteins are spun into continuous aligned filaments to yieldfood forms which simulate the fiber of natural beef. The document citesBelgian Pat. 634,140, U.S. Pat. Nos. 3,071,477 and 3,197,310 and CerealChem 43 (2) 195 (1966).

According to the '925 patent, the supporting fibers are present inamounts sufficient to render the products chew-resistant, self-containedand unit-integral and to enable them to remain in compacted, shaped andmolded form. The percent by weight of the indigestible fibers, or themixture of the indigestible and digestible fibers in a unilayer foodarticle may comprise up to about 50% or more, about 0.5–40%, about1–30%, of about 1–10%, but preferably from about 1–5%. The optimumamount depends on factors such as the thickness, length, etc., of thefibers and the desired chew-life.

It is noteworthy that the '925 patent does not discuss breakage orsplintering of the articles and the dangers they pose, nor does itaddress the objectives of the present invention. Rather, the '925 patentis primarily directed to pressed animal matter with added fibers thatare intended to enable the overall material to retain a structure.Further, the processing involved in the '925 patent is that of baking,in essence making cookies or biscuits (wherein the added fibers providea cohesiveness to the overall structure). Thus, the '925 patent dealsessentially with baking of compacted animal flesh or feed incorporatedwith structure-supporting fibers; in the preferred mode, the fibersmutually interlock so that a continuous fiber network spans the article.Regardless, the processing and nature of the materials involved ensurethat the fibers are of a static and correlated nature, closer infunction and, in fact, closer to being a second matrix which intertwineswith the first matrix.

SUMMARY OF INVENTION

According to the invention, a chewable, biodegradable article for pets(as a pet toy) comprises:

-   -   (a) as a matrix, a natural polymer, a synthetic organic polymer        or a mixture thereof;    -   (b) a natural or synthetic fibrous material that comprises        fibers and that is bonded chemically or physically with the        matrix material, and    -   (c) optionally, one or more microbe inhibiting agents that        inhibit the growth of microbes in or on the article    -   wherein, the presence of the fibrous material inhibits formation        of sharp edges upon breakage when the article is chewed. The        invention provides composite materials for safer and more        durable chewable articles for pets.

The above article of further may further comprise one or more of acompatibilizer, a plasticizer and an inert particulate.

A preferred natural polymer for the matrix of the above article is astarch-based polymer.

In the above article of, the fibers having an average length of betweenabout 0.1 μm and about 1200 μm, preferably between about 1 μm and about1000 μm, most preferably about 5–500 μm.

In the above article, the length-to-diameter ratio of the fibers isgreater than 25, and may be greater than 100. The weight fraction of thefibrous material relative to the weight of the article is between about1 percent and about 30 percent, preferably between about 2 percent andabout 15 percent.

The fibrous material in the above article may be a natural fibrousmaterial, for example, comprising a collagen, a cellulosic, apolysaccharides, flax, hemp, cotton, wool or a mixture thereof. Thefibrous material may also be a synthetic fibrous material, for example,a poly(alpha-hydroxy acid), nylon, polyester, or polyolefin, or even aninorganic oxide fiber.

In contrast to the '925 patent, the present invention utilizes polymericmaterials which are processed in radically different way (polymer meltprocessing) than are the “biscuits” of the '925 patent (baking).Processing in the present invention involves elevated temperatures,shear rates, and pressures, resulting in final articles with profoundlydifferent microstructural characteristics, such as a., relative lack ofcorrelation in spatial distribution of the fibers (no spanningstructures or clumping). Furthermore, the nature of the matrix in thepresent invention differs fundamentally from that in the '925 patent inthat it is self-supporting. Thus, the polymers of the present chewablearticles possess great cohesiveness and structural integrity on theirown (without added fibers). Fibers (and/or other materials) are added tothe articles of the present invention (1) to affect favorably the natureof the breakage processes and (2) to improve the “mouth-feel”, all theewhile without sacrificing desirable mechanical properties anddegradability.

The above article preferably comprises one or more microbe inhibitingagents.

Also provided is a process for making a composite material that isformable into the above article, comprising combining the polymer ormixture of polymers, the fibrous material and, optionally, the microbeinhibiting agent, under conditions that result in a material that doesnot tend to splinter or form sharp edges when formed into a chewablearticle and subjected to chewing.

A process for manufacturing a chewable article comprises making theabove composite material and forming the material into the article.

DETAILED DESCRIPTION

The present invention provides safer chewable articles for animals byincorporating binding material into the articles which (a) increasedurability, (b) decrease the tendency for pieces to detach, and (c)inhibit formation of sharp edges upon breakage.

The degradable chewable articles of this invention are comprised ofnatural polymers, synthetic organic polymers or mixtures thereof.

A common class of biodegradable polymers is starch-based. Pure starchpolymers do not possess the desired properties as they are brittle andare unduly affected by moisture. They are therefore commonly blendedand/or reacted with other polymers. U.S. Pat. No. 5,321,064 describes aclass of biodegradable polymers in which starch is reacted withsynthetic polymeric material such as polyethylene, polystyrene,polypropylene and polyvinyl chloride. U.S. Pat. No. 5,409,973 describesa class of materials based on starch and an ethylene copolymer. U.S.Pat. No. 5,360,830 describes a similar material produced in expandedform. U.S. Pat. No. 5,459,258 describes a class of biodegradablematerials based on the combination of hydrophobic polysaccharides, onethermoplastic and the other non-thermoplastic.

Biodegradable starch-based resins are available commercially from anumber of manufacturers, such as Starchtech™, Novamont™ and ArizonaNatural Materials™ Starchtech™ sells a series of such polymers under the“Re-NEW™” trade name. Novamont™ offers several classes of such polymersunder the trade name, “Mater-Bi™.”

A starch-based chewable article reinforced with natural fibers asdescribed below is a preferred embodiment of this invention.

Biodegradable synthetic organic materials of poly(α-hydroxy acid) classincluding poly(lactic acid) (PLA), poly(glycolic acid) (PGA) resins, aswell as poly lactide-glycolide (PLGA) copolymers have numerous desirableproperties. (See: Ratner, BD et al., Eds., Biomaterials Science,Academic Press, New York, 1996, p. 64; Naitove, M., Plastics Technology,March 1995, p. 15.) A variety of commercial grades are available fromCargill, under the name “EcoPLA™,” and also from various biomedicalsuppliers. Adjustment of the PGA:PLA ratio in a material can be used tofine-tune the texture, degree of hydrophilicity and rate ofbiodegradation. For example, PGA is more hydrophilic than PLA, so thatincreasing the PGA content will increase the hygroscopic property(uptake of water, saliva, or any other fluid). In addition, although PGAis highly crystalline, which generally slows its degradation, it becomesmarkedly less crystalline, and more degradable, when blended with PLA.

Materials based on polyhydroxybutyrate (PHB) are also attractive. Oneexample, available commercially under the name Biopol™ comprises a blendwith 3-hydroxyvaleric acid (PHV). PHB is generally highly crystalline,inflexible, and difficult to process. Blending with PHV diminishes thecrystallinity, resulting in more flexible, more easily processedmaterials.

Polycaprolactone, either pure or blended with other materials, is agenerally attractive degradable material that has found uses in medicalapplications such as sealing materials for wounds.

Other attractive degradable materials include, the poly(amino acids),the polyanhydrides, poly (ortho esters), and polyphosphazenes.

The nature of the present matrix differs fundamentally from the priorart in that it is self-supporting, meaning that it needs noreinforcements or other aids (such as fibers) in order for it to possesssubstantial structural integrity. Thus, the present matrix materialsform “respectable” materials in their own right (in contrast to those,for example, disclosed in U.S. Pat. No. 4,364,925.

The polymer in the matrix is often combined with inert particulates,compatibilizers, plasticizers, etc. For a general reference, seePlastics Additives and Modifiers Handbook, J. Edenbaum, ed., Chapman andHall, Great Britain, 1996, which is incorporated by reference in itsentirety.

It is preferred to include one or more antimicrobial agents to inhibitthe growth of mold or other microbes in the articles.

More durable and safer degradable chewable articles for animals areproduced by including a fibrous material, preferably a natural fibrousmaterial, in the article's formulation.

In preferred cases, the fibrous material forms chemical or physicalbonds with the host material (the “matrix”). Chemical bonds aregenerally covalent or ionic bonds—powerful short-range interactions.“Physical” bonds generally refer to longer range interactions (e.g.,dispersion forces) or structural interactions such as interlockingbarb-like structures, interpenetration (like wood glue), etc. Bothclasses of bonding are well-known in the art of adhesion engineering.

Such fibers resist propagation of a clean breakage plane, therebyinhibiting formation of sharp edges upon breakage. This not onlyinhibits breakage but also forces those breaks that will necessarilyoccur to have a “bumpy” profile, thereby minimizing sharp edges.

The fibrous materials can be either of natural or synthetic origin. Forformulation of articles that are relatively more (or more rapidly)degradable, natural fibrous materials are preferred because of theirdegradability upon exposure to saliva, enzymes, and other substanceswith which they come in contact during the acts of chewing anddigestion. Also preferred are biodegradable synthetic polymer fiberssuch as the poly(α-hydroxy acids). In addition, presence of naturalfibers may be preferred by consumers as they are perceived as beinghealthier for the animal.

In a preferred embodiment, fibers are incorporated into the chewablearticles along with an a microbe-inhibiting (“MI”) agent or compound. AMI compound is one that inhibits the growth, proliferation, spread, ofany of a number of microorganisms, most importantly fungi (especiallymold and yeast) and bacteria as well as algae, protozoa and variousmicroscopic parasitic organisms. The most preferred compounds act in amanner that is not selective for any particular organism, but rather areinhibitory to a broad spectrum of microbial agents. The MI compound canact by any mechanism to inhibit growth of the organisms, whetherbiostatic or biocidal. The preferred compounds are not required to havea particular inherent level or threshold of activity to be useful inaccordance with this invention. In general, the preferred MI compoundsare not the highly selective antibiotics of the type used in humanmedicine. Presence of a MI agent or compound is especially importantwhen using a natural or otherwise biodegradable material either as thematrix or as a binding element since such a material is especiallysusceptible to microbial invasion and degradation.

MI compounds useful in the present invention are described in moredetail in commonly assigned application U.S. Ser. No. 09/513,703, filedFeb. 25, 2000, now U.S. Pat. No. 6,566,419, which also describesformulations and processes for incorporating these compounds. Below is anon-limiting description of some of these compounds.

A preferred MI compound is diiodomethyl-p-tolylsulphone (“DIMTS”).Paulus, W., Microbicides for the Protection of Materials, Chapman &Hall, 1993, which is hereby incorporated by reference, describes thisand other biocidal and biostatic agents. This compound possesses a broadspectrum of anti-microbial activity, and is most active against fungi(including yeast) and algae. DIMTS is especially preferred in articlesthat may be partially or wholly digested.

DIMTS can cause yellowing in the final article, and if this is deemedunattractive, color suppressants can be added. DIMTS melts at about 157°C. It is relatively insoluble in water (0.0001 g/L at 25° C.). Acetone(350 g/L at 25° C.) and ethanol (20 g/L at 25° C.) are preferredsolvents. DIMTS is generally stable over a pH range of about 4–10. Apreferred form of DIMTS is the product Ultrafresh UF-95™, available fromThomas Research Associates. The concentration of UF 95™ in the finishedproduct should be between about 0.001% to 3%, preferably between about0.01% and 1% by weight percent. (Unless otherwise specified, allconcentrations disclosed herein are given in weight %).

Triclosan (2,4,4″-trichloro-2-hydroxydiphenylether), another preferredMI compound, is sold by Ciba-Geigy under the trade name Irgasan DP-300™. It can be obtained as a crystalline powder or as a liquidconcentrate. It is also available from Thomas Research Associates underthe trade name Ultrafresh NM-100 ™ in a commercial form ready forcompounding. Unmodified triclosan is insoluble in water;

-   -   sparingly soluble in dilute alkali solution; and soluble in        ethanol. It melts at about 60° C., and decomposes at about        285° C. It has an LD 50 oral toxicity of >5000 mg/kg for dogs.        It is non-mutagenic, non-teratogenic and has good skin        compatibility. Data for triclosan, along with that for many        other MI agents, are given in Paulus, supra.

Ultrafresh NM-100 ™, a preferred form of triclosan, is added inquantities to achieve a final concentration in finished product betweenabout 0.001% and 2%, preferably between about 0.004% and 0.3% by weight.

Bacticlean™ (alcohol ethoxylate 5–10%, benzalkonium chloride 1–5%, alkyldimethylamine betaine 1–5%, alkylamine dicarboxylate sodium 1–5%)(Allied Resinous Products, Inc., Conneaut, Ohio) is a preferred MI“cocktail,” i.e., a combination of compounds that work together tocreate broad-spectrum protection against microbial growth. Bacticlean™is particularly preferred when processing with polyolefins.

Other preferred MI compounds include Vinyzene™ (OBPA(10,10″-oxy-bis-phenoxarsin)) (Rohm and Haas Company); Intercide™ (atributyltin derivative) (AKZO Nobel, Inc., Chicago, Ill.); Fungitrol™(N-(trichloromethylthio)phthalimide) (International Specialty ProductsCorporation, Wayne, N.J.). (N-(trichloro Cunilate™(copper-bis-(8-hydroxyquinoline) (Rohm and Haas Company); Vancide™ (zincdimethyldithiocarbamate) (R.T. Vanderbilt Company, Inc., Norwalk, Conn.)(N-tri Micro-Chek (2-N-octyl-4-isothiazolin-3-one) (Ferro Corporation,Cleveland, Ohio); Zinc Omadine (a zinc complex of pyrithione); andApacider™ (silver hydroxyapatite) (Sangi Co., Ltd.; Sangi America,Thousand Oaks, Calif.).

In many cases, consumers may prefer articles that include or have beentreated with natural MI agents. Garlic and turmeric are preferredsources of such materials, e.g., in the form of extracts orconcentrates, but other natural spices or additives known in the art canbe used as well.

A diffusible MI agent (such as triclosan or DIMTS) will diffuse into thesurrounding material, thereby imparting the MI property to the material.This will generally diminish biodegradability of the article as the MIagent neutralizes or otherwise inhibits any of a number of biodegradingmicrobes, but will generally not diminish the degradability that resultsfrom the chewing action (e.g., the biodegradation caused by saliva,digestive enzymes, and aqueous fluids including water). Thus, thisselective action of the MI agents can be exploited to fine-tune thedegradability and sensitivity of the present chewable articles.

In the case of a strongly bonded or relatively non-diffusing MI (such asDow Corning 5700), the MI property will remain only with the fibers,which will resist biodegradation, but will not be imparted to the restof the article. This property is preferred when a more biodegradableproduct is desired.

Whether natural or synthetic, the fibrous materials used herein shouldbe in the form of fibers of discrete lengths rather than continuousfilaments. Useful fibers range in length from fractions of a millimeterto centimeters. Preferred fiber diameters are in the range of about0.1–1200 μm, more preferably about 1–1000 μm most preferably about 5–500μm. Preferred length-to-diameter (L/D) ratios exceed 10, preferablyexceed 20, and most preferably exceed 25. Fibrous materials having L/Dratios exceeding 100 or even 1000 are also contemplated.

The fibrous materials are usefully employed in weight fractions(relative to the weight of the articles), ranging from 1 percent to 30percent, preferably from 2 percent to 15 percent.

For articles having dimensions with a significant aspect ratio, e.g.,articles shaped like bones for dogs, it is preferred that a significantportion (but not necessarily all) of the fibrous materials be orientedalong the long dimension of the article, since this will provideresistance to crack propagation in response to the principal stressesimparted by chewing.

A wide range of natural fibrous materials may be used in the presentinvention. Preferred natural fibrous materials include collagens,cellulosics, polysaccharides, flax, hemp, cotton, wool or mixturesthereof. The collagen is preferably from an animal source.

A preferred natural material is cotton fiber. Cotton fiber may beobtained pre-compounded in commercial pellet form, e.g., inpolypropylene or polyethylene pellets, where the cotton is typicallyseen as a lightweight filler. In a preferred embodiment, cotton-loadedsynthetic polymer pellets are blended with a natural material, such as astarch-based material, and the resulting articles are molded into adesirable shape. Other synthetic polymers may also be included, alongwith compatiblizers or coupling agents.

Cotton fibers, cut into the appropriate lengths, may also simply becompounded with the base material as it is being pelletized.Alternatively, the fiber may be mixed with the compounded pellets in thehopper of an injection molding apparatus.

Synthetic fibrous materials may also be used. Useful synthetic fibrousmaterials include both organic and inorganic fibrous materials, withorganic materials preferred. Examples of useful inorganic syntheticfibrous materials include carbon and glass, particularly fibrous glassesthat are more water soluble than conventional fiberglass. Such ascompositions based on modified sodium silicates. Nonlimiting examples oforganic synthetic fibrous materials include nylons, polyesters andpolyolefins. Preferred synthetic organic fibrous materials are thepoly(α-hydroxy acids) such PGA, PLA and PLGA.

When using synthetic fibrous materials, a bonding agent is preferablypresent to encourages at least partial physical or chemical bonding ofthe fibrous materials with the matrix. The bonding agent can be adiscrete chemical species which promotes bonding, such as asiloxane-based coupling agent, or may represent chemical units in thefibrous materials for which there exist complementary chemical units inthe matrix or which have inherent bonding capabilities with chemicalgroups in matrix materials, e.g., the amide groups in nylon fibers.

Bonding may also be promoted by using maleated fibers (or other discretebinding elements) and/or the maleated matrix material.

The matrix can be wholly natural, wholly synthetic or a blend (eitherreactive or non-reactive) of at least one natural material and at leastone synthetic material.

Preferred synthetic matrix components include polyolefins (e.g.,polyethylene, polypropylene, polyisoprene, polystyrene), ethylenecopolymers (e.g., poly-ethylene-vinyl alcohol, poly-ethylene-acrylicacid), polycapralactone, PGA, PLA and PLGA copolymers, polyurethanes,particularly polyether urethanes, polycarbonates, polyamides,polyesters, etc. Forms of these polymers that are rendered more reactiveare preferred in cases where the natural matrix component is notparticularly reactive or is otherwise less amenable to chemical orphysical bonding. One means of accomplish such heightened reactivity isby forming the polymer grafted or otherwise incorporated with maleicanhydride.

Preferred natural matrix components include starcheous materials,proteinaceous materials, lignin and lipids. Starcheous materials can beobtained from potatoes, corn, wheat, rice, tapioca, etc. Preferredstarcheous materials are derived from corn, wheat, and/or potatoes.

Proteinaceous materials can be derived from a variety of animal andvegetable sources well-known in the art. Preferred proteinaceousmaterials for use as matrix components are gelatins, casein, andcollagens. Lipids can be derived from or incorporated as nuts, a milkproduct, vegetable oil or animal oil.

If the matrix material possesses substantial water or saliva sorptiontendencies, it is expected that, through use, the matrix may be tornaway from the binding material (e.g., the binding fibers) as the articleexpands. For this reason, when the water sorption tendency of the matrixmaterial is substantial, the binding material is preferably selectedfrom a group of materials with comparable or otherwise compatiblesorption tendencies.

When discrete fibers of relatively short lengths, e.g., 0.05–1 mm, areemployed as the binding agents, the chewable articles can be formed byknown techniques such as injection molding, compression molding,extrusion and rotomolding.

When discrete fibers of relatively long lengths, e.g., multiplemillimeters or more, are employed as binding agents, it is often usefulto form at least a portion of the chewable article using techniquesappropriate for long fibers, such as pultrusion. The portion of thearticle thus formed are then used as inserts in forming operations suchas insert molding.

The matrix of the present chewable articles may include a number ofinorganic or organic particulate materials, generally for the purpose ofmodifying and tailoring the (1) mechanical properties (2) theeaesthetics and (3) cost of the chewable articles. The preferred particlesizes of these particulate materials range from about 0.01 to about 100μm, preferably from 0.02 to 50 μm.

A preferred organic particulate material is dextran which can be used,inter alia, to modify the degradation rate of the article.

Useful inorganic particulate materials include materials that containsignificant amounts of (or that consist essentially of) titanium oxide,silicon oxide, carbon, aluminum oxide, hydroxide and oxy-hydroxide,calcium carbonate, feldspar, and kaolin. Because many such inorganicparticulate materials are obtainable at lower cost than the cost of theorganic constituents of the chewable articles, their use can lower theoverall cost of producing the article. In addition, they have greaterstiffness than the organic constituents, and can provide coloration andhiding power to the articles.

Generally larger particulates may be incorporated into the chewablearticles in an effort to engineer the “mouth feel,” which is thecombination of consistency and texture that create a particular setphysical sensations in the animal's mouth. For example, dogs often favora “bumpy” texture. Dispersing larger particulates such as sand or otherminerals throughout the article can enhance the bumpy texture.

Also useful are materials to modify the color, taste and aroma of thearticles. Dyes, primarily food dyes, are especially important.Taste/aroma agents include materials derived from animal fats or animalskins as well as garlic and other vegetable products. Salt and otherspices may also be used. Sorbitol can impart a pleasant taste inaddition to serving as a plasticizer. Taste agents may be incorporatedusing particulates as vehicles.

A chewable article of any desired shape or size is formed from thebiodegradable organic polymer compositions described above using methodswell-known in the art.

Having now generally described the invention, the same will be morereadily understood through reference to the following examples which areprovided by way of illustration, and are not intended to be limiting ofthe present invention, unless specified.

EXAMPLE

12 lbs. of wheat starch powder, 4.0 lbs of low density polyethylene, 2.4lbs. of sorbitol, 1 lb. of ethylene vinyl acetate grafted with maleicanhydride, 0.2 lbs of salt, and 0.4 lbs of fiber are blended and mixedtogether in a mixer. The fiber is comprised of cotton fiber of averagelength ˜1 mm, and average L/D ratio of ˜62.

The mixed batch is processed through an extruder at a temperature of300° F. A rotating blade at the exit die of the extruder cuts thematerial into pellets. The pellets are suitable for injection moldinginto an appropriate shape for a chewable article.

The references cited above are all incorporated by reference herein,whether specifically incorporated or not.

Having now fully described this invention, it will be appreciated bythose skilled in the art that the same can be performed within a widerange of equivalent parameters, concentrations, and conditions withoutdeparting from the spirit and scope of the invention and without undueexperimentation.

While this invention has been described in connection with specificembodiments thereof, it will be understood that it is capable of furthermodifications. This application is intended to cover any variations,uses, or adaptations of the invention following, in general, theprinciples of the invention and including such departures from thepresent disclosure as come within known or customary practice within theart to which the invention pertains and as may be applied to theessential features hereinbefore set forth as follows in the scope of theappended claims.

1. An article for chewing by pets, which comprises: (a) a matrix comprising a starcheous or proteinaceous material or mixtures thereof in combination with a poly(alpha-hydroxy acid) polymer or copolymer or mixtures thereof; (b) a fibrous material comprising collagen fibers or cellulose fibers dispersed throughout the matrix; wherein the article is formed by extrusion or injection molding.
 2. The article of claim 1 and further comprising one or more microbe-inhibiting agents.
 3. The article of claim 1 in which said fibers are bonded chemically or physically to said matrix.
 4. An article for chewing by pets, which comprises (a) a matrix comprising a starcheous or proteinaceous material or mixtures thereof in combination with a poly(alpha-hydroxy acid) polymer or copolymers or mixtures thereof; and (b) a fibrous material comprising fibers of poly(alpha-hydroxy acid polymer or copolymer or mixtures thereof dispersed throughout the matrix; wherein the article if formed by extrusion or injection molding.
 5. The article of claim 4 and further comprising one or more microbe-inhibiting agents that are active against at least three classes of microorganisms selected from the group consisting of bacteria, fungi, yeast, algae and protozoa.
 6. The article of claim 4 in which said fibers are bonded chemically or physically to said matrix.
 7. An article for chewing by pets, which comprises (a) a matrix comprising a starcheous or proteinaceous material or mixtures thereof in combination with a polyolefin or polyethylene copolymer and with a poly(alpha-hydroxy acid) polymer or copolymer or mixtures thereof; and (b) a fibrous material comprising fibers of collagen or cellulosic or mixtures thereof or poly(alpha-hydroxy acid) polymers or copolymers or mixtures thereof dispersed throughout the matrix; wherein the article is formed by extrusion or injection molding.
 8. The article of claim 7, wherein said matrix comprises a poly(alpha-hydroxy acid) polymer or copolymer or mixtures thereof together with a reactive combination of a starcheous or proteinaceous material with a polyolefin.
 9. The article of claim 7 and further comprising one or more a microbe-inhibiting agents that are active against at least three classes of microorganisms selected from the group consisting of bacteria, fungi, yeast, algae and protozoa.
 10. The article of claim 7 in which said fibers are chemically or physically bonded to said matrix.
 11. An article for chewing by pets, which comprises: (a) a matrix comprising a starcheous or proteinaceous material; and (b) a fibrous material dispersed throughout the matrix and comprising collagen fibers, polysaccharide fibers or cotton fibers, which are chemically or physically bonded to said matrix.
 12. The article of claim 11 wherein the matrix and fibrous material are formed into a shape suitable for chewing by pets by extrusion or injection molding.
 13. The article of claim 11 which additionally contains one or more microbe-inhibiting agents that are active against at least three classes of microorganisms selected from the group consisting of bacteria, fungi, yeast, algae and protozoa.
 14. The article of claim 13, wherein said microbe-inhibiting agent is selected from the group consisting of triclosan (2,4,4′-trichloro-2′hydroxydiphenol or ester thereof), diiodomethyl-p-tolysulphone, tri-n-butyl tin maleate, and 3-trimethoxy-silylpropyldimethyloctadecyl ammonium chloride, or mixtures thereof.
 15. The article of claim 11 which additionally contains one or more of a compatibilizer or compatibilizers, a plasticizer or plasticizers, a particulate material or materials, a color modifier or modifiers, a taste agent or agents and aroma modifier or modifiers.
 16. The article of claim 15, wherein said particulate material comprises particles selected from dextran, titanium oxide, silicon oxide, carbon, aluminum oxide, hydroxide and oxy-hydroxide, calcium carbonate, feldspar and kaolin, and mixtures thereof.
 17. The article of claim 15, wherein said taste agent is derived from plants.
 18. The article of claim 15, wherein said aroma modifier comprises an agent derived from animals.
 19. The article of claim 15, wherein said taste agent is incorporated using particulates as vehicles.
 20. The article of claim 11, wherein said starcheous material is derived from potatoes, corn, wheat, rice or tapioca.
 21. The article of claim 11, wherein said fibrous material comprises collagen fibers, cellulose fibers or mixtures thereof.
 22. The article of claim 11, wherein said fibrous material has an average fiber length between about 1 micron and 1000 microns, and wherein the length-to-diameter ratio of the fibers is greater than about
 25. 23. The article of claim 11, wherein said proteinaceous material is derived from animal sources.
 24. The article of claim 11, wherein said proteinaceous material is derived from plant sources.
 25. The article of claim 11, wherein the weight fraction of said fibrous material relative to the weight of the article is between about 1 percent and about 30 percent.
 26. The article of claim 11, wherein the article has a significant aspect ratio and a significant portion of said fibrous material is oriented along a long dimension of the article.
 27. The article of claim 11, wherein the fibrous material and the matrix are selected to resist propagation of a clean breakage plane, thereby inhibiting formation of sharp edges upon breakage.
 28. The article of claim 11, wherein said fibrous material is chemically treated to promote bonding to said matrix.
 29. An article for chewing by pets, comprising: (a) a matrix comprising a starcheous or proteinacous material in combination with a synthetic biodegradable polymer; and (b) a fibrous material comprising at least one of collagen fibers, cellulose fibers, polysaccharide fibers, cotton fibers and fibers of poly(alpha-hydroxy acid) polymers or copolymers.
 30. The article of claim 29 wherein the matrix and fibrous material are formed into a shape suitable for chewing by pets by extrusion or injection molding.
 31. The article of claim 29 in which said synthetic biodegradable polymer comprises a poly(alpha-hydroxy acid) polymer or a poly(alpha-hydroxy acid) copolymer.
 32. The article of claim 29 and further comprising one or more microbe-inhibiting agents that are active against at least three classes of microorganisms selected from the group consisting of bacteria, fungi, yeast, algae and protozoa.
 33. The article of claim 29 wherein said microbe inhibiting agent is selected from the group consisting of triclosan (2,4,4′-trichloro-2′hydroxydiphenol or ester thereof), di iodomethyl-p-tolysulphone, tri-n-butyl tin maleate, and 3-trimethoxy-silylpropyldimethyloctadecyl ammonium chloride, and mixtures thereof.
 34. The article of claim 29 and further comprising one or more of a compatibilizer or compatibilizers, a plasticizer or plasticizers, a particulate material or materials, a color modifier or modifiers, a taste agent or agents and aroma modifier or modifiers.
 35. The article of claim 34 wherein said particulate material comprises particles selected from dextran, titanium oxide, silicon oxide, carbon, aluminum oxide, hydroxide and oxy-hydroxide, calcium carbonate, feldspar and kaolin, and mixtures thereof.
 36. The article of claim 34 wherein said taste agent is incorporated using particulates as vehicles.
 37. The article of claim 29, wherein said starcheous material is derived from potatoes, corn, wheat, rice or tapioca.
 38. The article of claim 29, wherein said proteinaceous material is derived from animal sources.
 39. The article of claim 29, wherein said proteinaceous material is derived from plant sources.
 40. The article of claim 29, wherein said fibrous material has an average fiber length between about 1 micron and 1000 microns, and wherein the length-to-diameter ratio of the fibers is greater than about
 25. 41. The article of claim 29, wherein the weight fraction of said fibrous material relative to the weight of the article is between about 1 percent and about 30 percent.
 42. The article of claim 29, wherein said fibrous material is chemically or physically bonded to said matrix.
 43. The article of claim 29, wherein said fibrous material is chemically treated to promote bonding to said matrix.
 44. The article of claim 29, wherein the article has a significant aspect ratio and a significant portion of said fibrous material is oriented along a long direction of the article.
 45. The article of claim 29, wherein the fibrous material and the matrix ai-e selected to resist propagation of a clean breakage plane, thereby inhibiting formation of sharp edges upon breakage.
 46. The article of claim 1 and further comprising a particulate material.
 47. The article of claim 1 and further comprising at least one biocidal microbe-inhibiting compound.
 48. The article of claim 4 and further comprising a particulate material.
 49. The article of claim 4 and further comprising at least one biocidal microbe-inhibiting compound.
 50. The article of claim 7 and further comprising a particulate material.
 51. The article of claim 7 and further comprising at least one biocidal microbe-inhibiting compound.
 52. The article of claim 11 and further comprising at least one biocidal microbe-inhibiting compound.
 53. The article of claim 29 and further comprising at least one biocidal microbe-inhibiting compound.
 54. An article for chewing by pets, which comprises: a matrix comprising a starcheous material or proteinaceous material or mixtures thereof; a fibrous material comprising at least one of collagen fibers, cellulose fibers, polysaccharide fibers or cotton fibers, and poly(alpha-hydroxy acid) polymers or copolymers; and one or more biocidal microbe-inhibiting compounds.
 55. The article of claim 54 wherein said fibrous material has an average fiber length between about 1 micron and 1000 microns, and wherein the average length-to-diameter ratio of the fibers is greater than about
 25. 56. The article of claim 54 wherein the weight fraction of said fibrous material relative to the weight of the article is between about 1 percent and about 30 percent. 